The present invention relates generally to integrated circuits (ICs). More specifically, some embodiments of the present invention relate to a planar, monolithic, high-voltage (HV) IC having power field-effect-transistors (FETs) and/or bipolar power transistors having an HV diffusion connection.
In some applications, HV ICs typically include both HV and low-voltage (LV) transistors on a single monolithic die. HV transistors have larger dimensions than LV transistors in order to withstand the applied HV. This applies to HV transistors irrespective of whether they carry high-current (HC) or if they carry low-current (LC). Otherwise, HV transistors may have problems, such as junction or material breakdown, which causes uncontrolled currents to flow in the die. Such uncontrolled currents may lead to poor reliability or even catastrophic failure. Higher die area due to the inclusion of multiple, large HV-transistors drives higher die cost and lower yield. AN HV-LC transistor, although smaller in width than a HV-HC transistor (sometimes referred to as a “power transistor”), still takes up relatively large die area for the dimensions required for the HV diffusion if designed as a conventional stand-alone transistor. Consequently, there are usually fewer HV than LV transistors, and sometimes just one HV transistor, on the IC.
In a sub-group of these applications HV is supplied to a die through a HV-HC bipolar transistor or an HV-HC FET using an open collector or open drain configuration, respectively. Thus, the HV may be isolated to the particular large-area diffusion structure in a HV-HC transistor. LV may be supplied to a die through an additional external-supply. More desirably, to reduce overall system cost and complexity, LV may be supplied to the die by an on-chip, regulated, LV supply circuit drawing power for the entire IC through the power transistor from a singe external HV supply. Capabilities of such on-chip, regulated, LV supplies depend on circuits having HV-LC transistors in addition to the HV-HC, power transistor.
In such conventional HV ICs, providing an on-chip, regulated LV supply, which requires both HV-HC and HV-LC transistors, comes at the expense of relatively large die area, large cost, and low yield. Therefore, there is a need for new HV ICs that take up less die area while enabling circuits having multiple HV transistors.